Purification of bast fibers



Patented Sept. 15, 1936 roamcarron or BAST FIBERS George R. Bencraft, Philadelphia, Pa., assignor to Meigs, Bassett & Slaughter, Inc.,- Philadelphia, Pa., a corporation of Pennsylvania No Drawing.

Application September 24, 1934,

Serial No. 35,378 Claims. (Cl. 92-12) This inventiomrelates to the purification of bast fibers in general and also to the degumming of bast fibers of the structural type for the production of long, strong fibers suitable for use in the manufacture of so-called long-fiber paper".

The principal object of the present invention is to provide an improved process'of purifying bast fibers.

An important object of the invention is to provide an efficient and commercially practicable process of purifying bast fibers in general in order to produce textile fibers and the like.

Another important object of the invention is to provide an efiicient and commercially practicable process of purifying bast fibers of the structural type to produce long, strong ultimate fibers suitable for use in the manufacture of longfiber paper.

Other objects and advantages of the invention will become apparent during the course of the following description.

Where it is desired to produce textile fibers or the like from any bast fiber in general such as sisal, flax, ramie, or the like, the crude bast fiber to be treated may be cut to desired length and introduced into a digester with from 12 to 15 parts of water to 1 part by weight of fiber. From 15 to 40 per cent. of sodium sulfite on the weight of the fiber is dissolved in the water and the resulting mixture of fiber and sodium sulfite solution is digested under a. pressure of from 30 to 90 pounds per square inch. The digesting operation is continued for from 2 to 6 hours depending upon the character of the fiber under treatment and the pressure in the digester. Obviously, the lower the pressure the longer will be the digesting treatment.

After digesting for a desired period of time, the liquor present in the digester is drained off the fiber and an excess of water is-introduced into the top of the digester for the purpose of thoroughly rinsing the treated fibrous material.

After the rinsing operation, from 12 to 15 parts of water to 1 part by weight of ,fiber are then introduced into the digester and there is then pumped into the digester a soap solution, the

' soap solution preferably being made by the reacemploy an ammonium soapin the second boiling operation referred to above, other ordinary soaps may be employed'with some measure of success but since the results obtained by'the use of ammonium soap are greatly superior to those obtained with the use of other soaps, the employ-. ment of an ammonium soap is recommended.

After the boiling of the fibrous material in the 5 soap solution has been completed, the treated fibrous material is then washed thoroughly with an excess of water, after which the pufified fibers resulting from the treatment may be used as desired, for example, as textile fibers.

While the foregoing process is generally applicable to the treatment of any bast fiber, I have discovered that the operation may be simplified somewhat when the process is applied to the treatment of bast fibers of the structural type, 15 i. e. those bast fibers wherein the cellulose fibers are in the body of the stalk and not on the outside i of the woody center, such as manila hemp, pita,

pineapple, and New Zealand flax. I have found that when treating bast fibers of the structural type according to the modification of the process hereinafter described it is possible to separate the ultimate fibers without weakening or shortening the fibers to any appreciable extent with the result that the purified fibers are particularly suitable for use in the manufacture of so-called "lon fiber paper. While the resulting paper is generally similar to so-called Japanese tissue it is actually superior thereto. As is well known, the so-called long-fiber paper is particularly suitable for use for transfer paper, wrapping silver, surgical paper, etc.

In themodified practice of the process, bast fibers of the structural type. such as manila hemp, after being cut to suitable length if desired, are introduced into a digester in mixture with from 12 to 15 parts of water to 1 part by weight of fiber. From to 40 per cent. of sodium sulfite on the weight of the fiber is dissolved in the water. Thereafter the mass is boiled in the digester for from 4 to 6 hours at a pressure of about 60 pounds per square inch or above. After the digesting operation has been completed the liquor present is drawn oil and water is introduced into the upper part of the digester in order to thoroughly rinse the treated fibrous material. As a result of this treatment there may be produced from bast fibers of the structural type purified ultimate fibers which are approximately the same length and strength as the fibers before chemical treatment. The treated fibers may be introduced into a suitable paper making machine and long-fiber paper made therefrom.

While I have described in detail the preferred Pr ctice of my process it will be understood that the details of procedure may be varied considerably without departing from the spirit oi the invention or the scope of the subjoined claims.

I claim:

1. The process of purifying bast fibers which comprises boiling the same in a solution containing sodium sulfite, and thereafter boiling the treated fibers in a soap solution.

2. The process of purifying bast fibers which comprises boiling the same in a solutionof sodium sulfite, and thereafter boiling the treated fibers in a solution of ammonium soap.

3. The process of purifying bast fibers which comprises boiling the same in a solution of -sodium sulfite, separating the fibers from the treating solution, boiling the treated fibers in a soap solution, and washing the purified fibers.

4. The process of purifying bast fibers which comprises digesting the same in a solution of sodium sulfite, separating the treated fibers from the sodium sulfite solution, rinsing the treated fibers with water, digesting the resulting fibers in a solution of ammonium soap, and thoroughly washing the thus treated fibers.

5. The process of purifying bast fibers which comprises digesting the same in a solution containing from 15 to 40 per cent. of sodimn sulfite on the weight of the fibers for from 2 to 6 hours 10 monium soap, and thoroughly washing the thus 15 treated fibers.

GEORGE R. BENCRAFI'. 

